Question

Oxidation number of sodium in sodium amalgam is:
A. +2
B. +1
C. -2
D. Zero

Answer 1

Hint: - Before we start with the answer of the question, we must first understand the definition of amalgam, oxidation number.

Complete answer:
Oxidation number which is also called an oxidation State is the total number of electrons that an atom either gains or loses in order to form a chemical bond with another atom.
Sodium amalgam which is commonly denoted as $Na(Hg)$ is an alloy of mercury and sodium. The term amalgam is used for alloys, intermetallic compounds, and solutions which include both solid and liquid solutions in which mercury is a major component. In 1862 it was used as a reagent.
We must follow the chemical reactions by looking at changes in the oxidation numbers of the atoms in each compound during the reaction because oxidation numbers play an important role in the systematic nomenclature of chemical compounds. It can also be said that the oxidation number of an atom is the charge that an atom would have if the compound was composed of ions.
Amalgams are mixtures not compounds. So, there is no chemical combination of mercury and metal. Therefore, the oxidation state of metal in amalgam is always zero.

Hence, the oxidation number of sodium in sodium amalgam is zero.

Note: The oxidation state of sodium in $Na(Hg)$ is zero because it is a fused state of sodium in mercury which is a free state. And we must know that in a free state, the oxidation state of any element is always zero.